Using proton pump inhibitors in the first trimester of pregnancy could increase the chance that a baby will be born with a cardiac defect. In a 2010 retrospective study of over 200,000 women, those using proton pump inhibitors were twice as likely to have a child with a heart defect compared to those who did not take the drugs.

Prescription proton pump inhibitors currently on the market include Nexium, Dexilant, Prilosec, Zegerid, Prevacid, Protonix, and AcipHex. Proton pump inhibitors are also sold as over-the-counter versions under the names Prilosec OTC, Zegerid OTC and Prevacid 24HR. The drugs are approved to treat conditions such as gastroesophageal reflux disease (GERD), stomach and small intestine ulcers, and inflammation of the esophagus.

The 2010 study was conducted by researchers at the University of Pennsylvania. From a database of 208,951 pregnancies, the researchers found 2,445 cases of cardiac malformations in newborns and compared them with 19,530 matched controls. All of the newborns were registered between 2000 and 2008 in the Health Improvement Network, a database of information collected by general practitioners in the United Kingdom.

In women with children who were born with cardiac defects, 130 had taken proton pump inhibitors. Three types of birth defects were identified: septal defects, left ventricular defects, and right ventricular defects. The frequencies of those defects were comparable with those seen in the general United Kingdom population. Of the proton pump inhibitors studied, Nexium as associated with the greatest increase in risk for having a baby with a cardiac birth defect.

Since heartburn during pregnancy can be severe, the researchers said in a press release announcing their findings that physicians should weigh the benefits and possible risks of proton pump inhibitors on a case-by-case basis. They also suggested that other anti-reflux medications, such as H2 receptor antagonists, be considered first during pregnancy to minimize potential risks to infants.

Proton pump inhibitors, which have become extremely popular, have been linked to a variety of other side effects. Just last week, in fact, the U.S. Food & Drug Administration (FDA) warned that taking the drugs over the long term could result in low serum magnesium levels (hypomagnesemia), which can cause serious health problems including muscle spasm, irregular heartbeat and convulsions. The agency mandated that information about the potential risk of low magnesium be added to the WARNINGS AND PRECAUTIONS sections of the labels for all prescription proton pump inhibitors.

Last May, the agency also announced a label revision after it was found that long-term use of proton pump inhibitors, especially by women, could be associated with a long-term risk of certain fractures, including those involving the hip, wrist, and spine.